1. Field of the Invention
The present invention generally relates to the field of artificial bone synthesis based on hydroxyapatite binding sequences and peptides.
2. Related Art
A fundamental challenge in the field of biomineralization is to identify the short protein motifs which can specifically nucleate on or bind to the target materials. Although various protein matrices including collagens, osteopontin, and enamelogenin found in bone and dentin have been extensively studied and shown for specific nucleation of the target inorganic biominerals, understanding of the role of specific protein motifs are still limited. See L. Addadi, S. Weiner, Angew. Chem. Int. Ed. Engl. 31, 153 (1992); S. Weiner, L. Addadi, J. Mater. Chem. 7, 689 (1997); G. He, T. Dahl, A. Veis, A. George, Nat. Mater. 2. 552 (2003); C. E. Ye, K. R. Rattray, K. J. Warne, J. Gordon, J. Sodek, G. K. Hunter, H. Goldberg, J Bio. Chem. 278, 7949 (2003); and S. Mann, Biomimetic Materials Chemistry; VCH: New York, (1996). The long encrypted peptide chains hinder direct incorporation of protein matrices into functional building blocks in organic/inorganic hybrid composite materials.
One of the most promising methods to identify the specific short peptide binding motifs against the unknown inorganic or organic surfaces is phage display. See Whaley, S. R.; English, D. S.; Hu, E. L. Barbara, P. F. Belcher, A. M. Nature 405, 665 (2000) and Lee, S.-W.; Mao, C.; Flynn, C. E.; Belcher, A. M., Science, 296, 892 (2002). Phage display is a directed evolution process for identifying short peptide binding motifs against target materials. These binding peptides can potentially template the nucleation and growth of magnetic, optical, electrical materials, self-assemble these materials in various environments, or make them biocompatible. See C. Mao, D. Solis, B. Reiss, S. Kottmann, R. Sweeney, A. Hayhurst, G. Georgiou, B. Iverson, A. Belcher, Science, 303, 213 (2004); B. Reiss, C. Mao, D. Solis, K. Ryan, T. Thomson, A. Belcher, Nano Lett., 4, 1127 (2004). Phage display peptide libraries have emerged as a powerful method in identifying such peptide agonists and antagonists. See, for example, Scott et al. (1990), Science 249: 386; Devlin et al. (1990), Science 249: 404; U.S. Pat. No. 5,223,409, issued Jun. 29, 1993; U.S. Pat. No. 5,733,731, issued Mar. 31, 1998; U.S. Pat. No. 5,498,530, issued Mar. 12, 1996; U.S. Pat. No. 5,432,018, issued Jul. 11, 1995; U.S. Pat. No. 5,338,665, issued Aug. 16, 1994; U.S. Pat. No. 5,922,545, issued Jul. 13, 1999; WO 96/40987, published Dec. 19, 1996; and WO 98/15833, published Apr. 16, 1998 (each of which is incorporated by reference).
In such libraries, random peptide sequences are displayed by fusion with coat proteins of filamentous phage. Typically, the displayed peptides are affinity-eluted against an antibody-immobilized extracellular domain of a receptor. The retained phages may be enriched by successive rounds of affinity purification and repropagation. The best binding peptides may be sequenced to identify key residues within one or more structurally related families of peptides. The peptide sequences may also suggest which residues may be safely replaced by alanine scanning or by mutagenesis at the DNA level. Mutagenesis libraries may be created and screened to further optimize the sequence of the best binders. See Lowman (1997), Ann. Rev. Biophys. Biomol. Struct. 26: 401-24.